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69
Hverken i Mundskiven eller Tentaklernes Hud findes
Kalk.
Fordøielsesorganerne.
Tarmen danner de sædvanlige to Bøininger og gaar
da med en temmelig lige Rectum over i Kloaken, Fig. 15, c.
Denne er langstrakt oval, og fra dens forreste Del udgaar
paa hver Side af Rectum et Tarmappendix
(Respirations-rør), Fig. 15, d, 23. Det venstre, Fig. 15, e, 23, har en
temmelig kort, næsten nøgen Stamme, fra hvis forreste Ende
udgaar en kort Gren, der deler sig i utallige .større og
mindre Blærer, som antage Formen af en Drueklase. Det
høire Appendix, Fig. 15, J\ 23, er meget langt, fæster sig
paa 3 af Kalkringens Radialprocesser og er paa hele
Længden forsynet med større og mindre Blærer, der dels sidde
enkeltvis, dels i mindre Grupper med lange Mellemrum.
Forøvrigt er Tarnien i histologisk-anatomisk Henseende
ganske overensstemmende med den, der af os er beskreven
hos Troch. Thomsonii.
Det indre Skelet.
Kalkringen, Fig. 27, bestaar af 10 Stykker, 5
Radialstykker og 5 Interradialstykker, hvilke hos unge Dyr ere
bundne sammen med Bindevæv, saa de kunne skilles fra
hverandre, imedens de hos ældre Dyr ere fuldstændig
sammen voxede; Sømmene ere ganske forkalkede, saa, de enkelte
Stykker ikke kunne skilles fra hverandre, hverken med
Kniven eller kaustisk Kali.
Radialstykkerne, Fig. 27, a, ere 4""" lange og 2""
brede; paa Legemets udvendige Flade to fremragende
Kamme, Fig. 27, b, b, der paa den bagerste Trediedel ud»
vider sig i Bredden, saa at her fremkommer en Knude,
bagenfor hvilken Kammen bliver smalere. Den ene af
Kammene har paa den forreste Del en Fordybning, der
tjener til Fæstepunkt for Radialmuskelen, Fig. 27, c;
imellem begge Kammene er en temmelig dyb Fure, Fig. 27, d,
der optager en Ampulle. Fortil ende disse Kamme* i to
Fremstaaenheder, hvoraf den ene er lidt kortere, bredere
og mere afrundet, end den anden, og imellem hvilke findes
et halvrundt Indsnit, Fig. 27, e.
Ethvert Radialstykke har en bagerste, forlænget Del
(Processus), som paa sin yderste Ende er spaltet, Fig. 27,
/, og til hvis indre Flade Radialkarret er fæstet. De 4
af disse Processer ere omtrent lige lange, indtil 2mm\ men
den 5te, den nemlig, som svarer til Bugens midterste
Radialkar, er meget kortere, omtr. 1""". Alle disse
Processer vendo med deres spaltede Spidser saa stærkt indad •
Neither the oral disk nor the tentacles exhibit any
trace of calcareous deposit.
Digestive Organs. .
The intestine has 2 convolutions, and passes, with a
comparatively straight rectum, into the cloacum. fig. 15, c. The
latter organ is elongato-ovate in form; and from its anterior part
protends on either side of the rectum an intestinal
appendage (respiratory tube), figs. 15, d; 23. The left
appendage, tigs. 15, e; 23, has a comparatively short and almost
naked stem, from, the anterior extr.émity of which proceeds
a short branch, dividing into countless vesicles, varying
in size, which present the appearance of a cluster of
grapes. The right appendix, tigs. 15, /; 23, is exceedingly
long; it is webbed to three of the radial processes of
the calcareous ring, and furnished throughout its entire
length with vesicles, varying in size, some of which are
isolated and some arranged in small groups with considerable
interspace.
For the rest, the histological structure of the intestine
differs in no wise from that distinguishing the organ in
Troch. Thomsonii.
Calcareous Skeleton.
The calcareous ring, tig. 27, consists of 10 segments,
5 radial and 5 • interradial, which, in immature examples,
are webbed together by connective tissue, and thus admit
of being parted, whereas in full-grown individuals they
are connate ; the sutures are wholly calcined, and some of
the segments cannot be separated, either with a knife or
when treated with a solution of caustic potash.
The radial segments, fig. 27, a, are 4"" long and 2
broad; on the outer surface of the body are seen two
projecting combs, fig. 27, b, b, which expand at their posterior
third, and here accordingly there is a protuberance,
posterior to which the comb becomes narrower. One of the
combs has on its anterior part a depression, which serves
as a point of attachment for the radial muscle, fig. 27,
c; and between the two combs there is a rather deep
groove, fig. 27, d, for the reception of an ampulla.
Anteriorly, these combs terminate in two protuberances, one of
which is somewhat shorter, broader, and more rounded than
the other, and between which is seen a semicircular
incision, fig. 27, e.
Each radial segment has a posterior elongate part,
or process, cleft at the extremity, fig. 27, f, and to
the inner surface of which the radial vessel is webbed.
Four of these processes are about equal in length (2"*);
but the fifth — that corresponding to the medial radial
vessel of the belly — is much, shorter, about 1"". All
of the processes incline with their cleft extremities so
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